Gaga and Cooper star together in "A Star Is Born," which also marks Cooper's directorial debut.

The two play artists who meet and fall in love — Cooper as Jackson Maine, a rock star fighting an alcohol and drug addiction, and Gaga as Ally, a struggling singer.

Though Gaga and Cooper first officially met on the set of NBC's "Saturday Night Live" roughly five years ago, according to Vogue, it wasn't until Cooper caught a performance by Gaga in 2016 at a cancer benefit in Sean Parker's backyard that he thought she should be in the movie with him.

"She had her hair slicked back, and she sang 'La Vie en Rose,' and I was just...levitating," he told Vogue. "It shot like a diamond through my brain. I loved the way she moved, the sound of her voice."

Cooper called her agent and drove to her home the following day to discuss the movie.

"She came down the stairs and we went out to her patio and I saw her eyes, and honestly, it clicked and I went, 'Wow,'" Cooper said.

Gaga told Vogue that Cooper's depiction of romance and fame in the movie is authentic.

"They're both very complex, layered things, with a lot of emotional depth, and he captured that," she said. "This is what I think makes the film so successful: that it was so real. And I've lived it, so I can testify to that."